1. Field
The present invention is directed to a valve of a variable capacity compressor for vehicle, and more particularly to a suction valve of a variable capacity compressor for vehicle that may reduce noises created between a valve case and a spool valve.
2. Related Art
In general, a compressor for vehicular air conditioner compresses a coolant gas supplied from an evaporator using a dynamic force and transfers the compressed coolant gas to a condenser. Among the compressors, variable capacity compressors recently gain popularity, which control the inclined angle of a swash plate to change the discharging volume.
As shown in FIG. 1, a variable capacity swash plate-type compressor 100 generally includes a cylinder block 110 that includes a plurality of cylinder bores 112, a suction port 114, and a suction muffler chamber 116; a front housing 120 that is coupled with the cylinder block 110 before the cylinder block 110 to form a crank chamber 122; and a rear housing 130 that is located behind the cylinder block 110 and includes a suction chamber 132, a discharging chamber 134, and a discharging path 136.
A valve plate 140 is provided between the front housing 120 and the rear housing 130 and a coolant is introduced and discharged through the valve plate 140. As shown in FIGS. 1 and 2, the valve plate 140 is shaped as a circular plate and includes a plurality of coolant suction openings 140a that are arranged along an outer circular arc and a plurality of coolant discharging openings 140b that are arranged along an inner circular arc. A suction reed valve 142 is positioned in front of the valve plate 140 and a discharging reed valve 144 and a retainer 146 is sequentially positioned behind the valve plate 140. A one-way valve 150 is provided to prevent a coolant from flowing back to the front of the valve plate 140.
The variable capacity swash plate-type compressor 100 further includes a driving shaft 160 rotatably provided at the central portion of the cylinder block 110 and the front housing 120; a swash plate 170 connected to a rotor 172 mounted at the driving shaft 160 through a hinge portion 174 in the crank chamber 122 so that its inclined angle varies with the pressure of the crank chamber 122; and a plurality of pistons 180, each interlocking with the swash plate 170 through a shoe 176 and travelling forth and back in the cylinder bore 112 according to the rotation of the swash plate 170, thus sucking and compressing the coolant. A compression coil spring 178 is provided between the swash plate 170 and the rotor 172 to return the swash plate 170 to the original position.
As the driving shaft 160 and the swash plate 170 are rotated together, the coolant compressed in the cylinder block 110 is discharged to a condenser through the discharging path 136 and the discharged volume of the coolant may be varied by adjusting the inclined angle of the swash plate 170.
Although the swash plate 170 maintains the minimum inclined angle when the air conditioner of the vehicle is turned off, the angle does not become zero degree and thus the coolant is partially discharged from the variable capacity compressor 100 to the condenser even when the air conditioner is turned off. To prevent the coolant from being discharged when the air conditioner is turned off and prevent the discharged coolant from flowing back from the condenser to the variable capacity compressor 100, the one-way valve 150 is provided at the end of the valve plate 140.
The conventional one-way valve 150, as shown in FIGS. 2 and 3A, includes a valve sheet 152 having a coolant inlet 152a formed at the center; a valve case 154 provided over the valve sheet 152 and having a plurality of coolant discharging ports 154a along the circumferential surface; a spool valve 156 selectively opening/closing the coolant inlet 152a and the coolant discharging port 154a in the valve case 154; and a resilient member 158 provided between the valve case 154 and the spool valve 156.
As shown in FIGS. 3A and 3B, the valve case 154 includes four coolant discharging ports 154a, one facing another with respect to the central vertical axis of the valve case 154, and a vent hole 154b at the center of the top surface of the valve case 154 to prevent occurrence of back pressure. The valve case 154 further includes a guide portion 154c that extends downward from the inner surface of the top portion to guide and support the resilient member 158.
The spool valve 156 is shaped as a cylindrical structure whose bottom surface is closed and receives the resilient member 158 therein. The spool valve 156 is lifted up and down by pressure of the coolant in the valve case 154 to selectively open and close the coolant inlet 152a and the coolant discharging port 154a. 
In the conventional one-way valve 150, however, initial opening pressure was unstable due to a delay in opening time and leakage of coolant between the valve case 154 and the spool valve 156 when the spool valve 156 rises to initially open the coolant discharging port 154a, thus causing noises in pipes.
In the conventional one-way valve 150 shown in FIGS. 4A and 4B, immediately before the coolant discharging port 154a is initially opened, that is, when the pressure P of the coolant is equal to the spring force F of the resilient member, the spool valve 156 was swayed left and right due to back pressure of the coolant, thus creating a valve noise (low-frequency noise).
Also, as shown in FIG. 4C, the conventional one-way valve 150 has a structure in which back pressure exerted by the coolant discharging port 154a right after the coolant discharging port 154a is initially opened is difficult to release through the vent hole 154b provided at the center of the top portion. Furthermore, in the conventional one-way valve 150, a vortex flow generated while back pressure is released through the vent hole 154b caused a valve noise (high-frequency noise).
Korean Patent No. 10-0915713 (hereinafter, referred to as “Patent Document”) discloses a one-way valve that may reduce a valve noise created between a valve case and a spool valve. The one-way valve includes an asymmetrically-structured coolant discharging port at the central portion of the valve case so that one end of the spool valve is brought in tight contact with the inner wall of the valve case in order to reduce a valve noise. That is, the one-way valve disclosed in Patent Document may reduce a valve noise created when the spool valve crashes against the valve case under the situation that the spring force of a resilient member is equal to the pressure of a coolant.
In the one-way valve disclosed in Patent Document, increase in pressure at the valve inlet by a coolant opens the spool valve to adjust the flow rate of the coolant. The one-way valve has been mainly used in a case where the resilient member has a spring constant of 100 gf/cm or more. If the spring constant is set to be not more than 100 gf/cm in the one-way valve, low pressure is exerted to the valve case and this incurs inflow of more coolant. Accordingly, the spool valve was easily opened even when the coolant has low pressure, and thus, a noise was created at the early stage of opening the valve. Furthermore, under the condition that the spring constant is 100 gf/cm or less, back pressure was not swiftly released through the vent hole of the valve case, and this served as another source of valve noise.
As such, the one-way valve in Patent Document could not sufficiently address the problem with the valve noise in a case where the flow rate of coolant is high or the spring constant is not more than 100 gf/cm.
Accordingly, there is a need of providing a suction valve of a variable capacity compressor for vehicle that may reduce valve noise created at the early stage of opening the spool valve even when the spring constant of the resilient member as used is 100 gf/cm or less and smoothly release back pressure to decrease valve noise.